They tried to hit me with "late fees" when I returned the car ~4-5 hours late, twice, when I was still within the 24-hr period when a new "day" would start. So now, I just book everything in 24 hour increments. If there's a chance that I'll stay later than my usual 4-days, I'll book for a month & return it in 5-6 days. There has never been an "early fee", so I'll just book the crap out of their system and give it back whenever I feel like it.